This invention relates generally to a clutch mechanism and specifically to a range limiting dual direction slip clutch for use with an automotive vehicle windshield wiper assembly.
It is customary for automotive vehicles to have one or more windshield wiper assemblies. Conventional assemblies include rubber wiper blades mounted upon claw brackets that are pivotally attached to wiper arms mounted upon a rotating shaft. A variety of methods have been utilized to activate the rotating shafts including using an electric motor which actuates a series or parallel-coupled four-bar linkage mechanism.
Utility vehicles and minivans often employ a window wiper assembly for cleaning the rear window. Typically, these types of rear window wiper assemblies include a wiper blade mounted upon a bracket which is coupled to a wiper arm. The wiper arm is attached to a wiper shaft rotatably driven in a cyclicle oscillating manner by a helical gear. A reversible, fractional horsepower, directional current electric motor serves to actuate the helical gear through an armature shaft-mounted worm gear enmeshed therewith. An example of this type of rear window wiper arrangement is disclosed in U.S. Pat. No. 5,519,258 entitled "System and Method for Controlling Vehicle Liftgate Window Wiper".
It is also well known in minivans, station wagons, and sport-utility vehicles to employ a rear window release lock or latch that is actuated by a solenoid. The latch can be unlocked to allow for upward pivotal movement of the rear window in relation to the otherwise stationary liftgate. A separate liftgate lock can be mounted upon the liftgate door for fastening the liftgate to the body of the vehicle thereby preventing inadvertent opening of the liftgate. This liftgate lock is traditionally operated by manual key or handle rotation, or more recently through a separate electric motor or solenoid. It is also well known to provide a separate electric motor to operate a pump for providing fluid under pressure to the rear window for cleaning the same.
Separate motors or solenoids are commonly required to actuate the aforementioned locks, the wiper, and fluid pump. However, having multiple motors has increased vehicle weight and cost while further proving difficult to package within the often small spaces provided. This because the window wiper mechanism, rear window lock and liftgate lock and windshield wiper pump, as well as their motors, are all incorporated within the pivoting liftgate.
To overcome the aforementioned problems, a single electromagnetic device has been provided that selectively operates an intermittent motion mechanism coupled to a window wiper, a door lock, a window release lock, and the like. An example of such improvements can be found in WO 96/33891 entitled "Multi-Functional Apparatus Employing an Intermittent Motion Mechanism", WO 96/33892 entitled "Control System for an Automotive Vehicle Multi-Functional Apparatus", and WO 96/33893 entitled "MultiFunctional Apparatus Employing an Electromagnetic Device". These devices generally employ a geneva or starwheel-type mechanical construction for imparting rotational movement to an output pinion. WO 96/33891 specifically teaches an electric motor driving a main gear having a plurality of output devices connected thereto. Each such output device can be selectively activated depending upon whether the driver desires to activate the windshield wipers, liftgate release/lock mechanism, rear window release lock mechanism, or the like.
The aforementioned systems employ a direct connection from the output pinion to the windshield wiper arm. During inclement weather conditions, the wiper arm can become stuck, for example, when ice builds up on the windshield, thus causing the wiper arm to stop. Also, if a person were to grab the wiper during operation, the motor would be directly impeded. With conventional wiper mechanism designs, these conditions could stall the drive motor strip components, including gears, bend, or even break the wiper arm. If the arm stops, a driver would be prevented from utilizing the liftgate release lock mechanism or the rear window release lock mechanism until the windshield wiper becomes unstuck. Thus, it is desirable to disengage the wiper arm from the electric motor during certain conditions in order to allow other features to be utilized in the vehicle that are propelled by a common electric motor.